Key points



Beneficial actions and effects

Resistance (by bacteria)

Adverse effects


Although there are no (formal) subclasses of tetracyclines, there is natural grouping based on lipid solubility. Older tetracyclines (oxytetracycline, tetracycline, chlortetracycline) have the lowest lipid solubility. Doxycycline is intermediate and minocycline is the most lipid soluble. This MOSTLY affects the likelihood that the drug will reach the bacteria in adequate concentration. This is especially important for intracellular infections but it may also be important for antibacterial treatment in reserved spaces (e.g., prostatitis).

Available agents


  • most available products (among the tetracyclines)
  • multiple injectable dose forms
  • LA products really better tolerated dose forms (larger dose / volume)


  • feed
  • capsules
  • opthalmic
  • limited injectable forms
tetracycline capsules, USP


  • almost exclusively feed and water administration
  • will sick animals consume adequate doses?
chlortetracycline soluble powder


  • oral
  • injectable forms not particularly suitable
    • injectable form used in europe for pet birds not available in US
    • muscle damage in pet birds
    • iv use not recommended in horses
doxycycline capsules, USP

minocycline (oral)

  • most lipid soluble of the class
  • should be preferred (among tetracyclines) for intracellular and reserved space infections
  • substitute for doxycycline in some therapies depending on price and availability
minocycline hydrochloride capsules, USP